If it were transcribed phonetically from Polish, I'd guess at Blaczkowski or Blachowski. In Polish, a 'c' can have a guttral 'ch' sound, as in the scottish 'loch'
I have a book (Polish Surnames, Origins and Meanings), which shows that 10 years ago, there were 747 people living in Poland with the name Blachowski and 235 with the name Błachowski.
The name originates fron 'sheet metal, or tin', suggesting that in generations past the family were metal workers.